The present invention relates generally to milling machines and more particularly to milling machines for asphalt, concrete, and other road surface materials so that a worn surface may be removed and replaced with new material. Milling machines of this type have, in the past, had fixed width cutters. My invention is an improvement of the known machines by providing a cutter that can be readily and easily converted from one width to another and particularly, to provide for a cutting width of 2', 3' or 4' (or any other selected increments between 24" and 52") with minimal down time in the operation of the machine and with minimal man power required to make the conversion. Further, my invention is designed to enable each cut to be made at the optimal outside location of the machine so that the machine can make different width cuts directly adjacent bridge abutments, embankments, and severe slopes (such cuts being generally referred to in the industry as "flush cuts" and the practice as "flush cutting").
It will be appreciated by those skilled in the art that highways, parkways, roads and streets that serve as thoroughfares for motor vehicle travel in this country are subject to tremendous wear and tear and eventual decay. Also, there are often occasions when roads and highways must be improved by widening them or adding lanes in order to accommodate increased motor vehicular traffic. Such roads and highways are generally paved with concrete or asphalt. In order to repair them, it is usually necessary to remove the concrete or asphalt, or to remove at least a portion of the concrete and asphalt, requiring a cut of several inches of depth.
When existing roads are be repaired, it is necessary to remove the material of the portion of the road or highway passing beneath overpasses so that when new material is paved over the existing surface, the height of the road will not be increased and thereby reduce the clearance between the road and the underpass. Such clearances are generally specified to reasonably close tolerances and if the repair of the road increases the height of the road by adding new material to it, after several repairs, the clearance between the road and the underpass will be reduced to a point that certain traffic, particularly tractor trailer rigs and the like would crash into the lower side of the overpass if the material of the road was not removed prior to repaving. Likewise, on bridges and overpasses, when roads are repaired, it is necessary to remove the existing material before applying a new surface in order to reduce the weight on the bridge or overpass, such bridges and overpasses normally having been engineered to accommodate a specified weight limit. Continually adding new weight by adding the weight of resurfacing material may exceed the limitations of such bridges and overpasses when the weight of vehicles traveling over those bridges and overpasses is added to the equation.
Finally, in the repair of the existing roads and highways, there are numerous bridge abutment, guard rail and other traffic control barriers along the roads. It is important to be able to remove the asphalt or concrete as closely adjacent such barriers as possible through automatic equipment and milling machines of the type to which this invention is directed so as to eliminate manual labor in removing the material directly adjacent such barriers. Similarly, it is important to be able to use milling machines to remove material adjacent embankments and slopes without having to use manual labor for that job.
In the improvement of existing highways and roads, particularly when highways and roads are being widened, cuts have to be made in the existing shoulder of the old road in order to provide for a base of rock and other compressed material and a layer of asphalt or concrete over the base material. The finished job must have the widened portion of the highway be at the same level as the refinished existing highway. These cuts often have to be made in cities adjacent sidewalks, over existing roads adjacent bridges and other areas where embankments, slopes, and highway appurtenances require that the machine cut at its extreme most outside edge because there is no room for the tracks of the machine beyond the cutting point. It is appropriate to note at this point of discussion of the background of the invention that in machines of this type, the power train for driving the cutter is generally positioned on what is referred to as the "inside" of the machine because if it were located on the "outside" of the machine, it would extend beyond the cutting edge and limit the ability of the machine to make flush cuts. Further, practical aspect of the design of machines of this nature require that the drive train provide power to the cutter via an axil passing through the cutter itself and drive the cutter from the inside of the machine.
In machines currently available in the marketplace, such as machines available through Applicant's assignee, Wirtgen America, Inc., Nashville, Tenn., for the milling machine to make cuts of varying width, the entire cutter has to be removed and replaced with a different sized cutter. Such devices include the Wirtgen 1900 DC cold milling machine which is readily available on the marketplace and which is illustrated and described in the sales brochure identified in the bibliography attached hereto and a copy of which is supplied with this application and incorporated herein by reference.
Cold milling machines are the type that my invention is designed to modify fall in the category of road building or material handling equipment. The machines themselves may cost as much as $750,000 and the cost of a milling drum with cutter elements can be as much as $200,000. Thus, while there have been provided machines that allow different cutting widths by interchanging the milling drums, such devices require that the operator have on hand two or more milling drums and if the operator is required to purchase several milling drums, the cost of each additional drum is significant. Further, in existing equipment, conversion from one width to another by exchanging one milling drum for another requires several men because of the size and weight of the equipment and may take as much as two full days to accomplish. One days down time for a machine of this type is a significant economic loss to the contractor because it slows the completion of the job and requires the use of expensive man power.
What is needed then is a method of conveniently and quickly changing the width of cut of a milling drum in a cold milling machine designed for making cuts of a depth up to 12" in highway concrete, asphalt and rock base and in widths varying from 2' to 4'. Such a device is presently lacking in the prior art and in the marketplace.
It is therefore an object of the present invention to provide a new and improved cold milling machine that can be readily converted from one cutting width to another with use of minimum man power and time.
It is another object of the present invention to provide such an improved cold milling machine that will allow cuts of up to 12" deep substantially in line with the outside of the machine.
It is a further object of the present invention to provide an improved machine with a moldboard or scraper that can be varied in width to accommodate varying widths of the cutter and can be varied in height along its width to accommodate the depth of cut being performed by the machine.
It is yet another object of the present invention to provide such an improved cutter where the change in the width of the cutter can be accomplished by a single workman using simple hand tools and accomplished within 2-3 hours.
Having described generally the objects of the present invention, Applicant's invention will be better understood when considered in light of the accompanying drawings and the following description of the preferred embodiment.